ALERT SERVICE BULLETIN

MBB BK117 C-2

CHANGE INSTRUCTION NO. 2 FOR MBB BK117 C-2-04A-005

2010-04-28 PAGE 1 of 1

Date: First issue: 2009-06-08

Revision 01: 2009-06-22

Revision 02: 2010-04-28

Please replace Alert Service Bulletin MBB BK117 C-2-04A-005 with Revision 02.

With Revision 02 the following bevel gear S/Ns are added: S/N 1039, 1065, 1113, 1129 and

S/N 1156.

If the previous issue of this Alert Service Bulletin has already been accomplished, the

intermediate transmission must be checked for the installed bevel gear S/Ns that have been

added with Revision 2.

ALERT SERVICE BULLETIN

MBB BK117 C-2

MBB BK117 C-2-04A-005

PAGE 1 of 5

2009-06-08

REVISION 02, 2010-04-28

Airworthiness Limitations – Tail Rotor – Reduction of the life time of

certain bevel gears

1. Planning Information

A. Effectivity

(1) Helicopters affected: All MBB BK117 C-2.

(2) Components affected: Intermediate transmission P/N 4639 002 007 with bevel

gears P/N 4639 310 065 of serial numbers i.a.w. attached

Table 1.

(3) Spare Parts affected: Intermediate transmission P/N 4639 002 007 with bevel

gears P/N 4639 310 065 of serial numbers i.a.w. attached

Table 1.

B. Concurrent Requirements

Not applicable.

C. Reason

On bevel gear production batch numbers tooth foot fillets had been detected which were

below the minimum values required in the design documents. Calculations have shown that

this decreases the life limit of the bevel gears. Therefore, with this Alert Service Bulletin the

life limit of the affected bevel gears 4639 310 065 is reduced.

D. Description

Determine the current Flight Hours (fh) of the affected bevel gears. Enter changed life limits

in the list of life–limited parts and in the log card. Determine the remaining life of the bevel

gears and if necessary replace the bevel gears (intermediate gear box). Fill out reply form

sheet and send it to ECD.

E. Compliance

(1) The current life limits of the affected bevel gears 4639 310 065 must be determined

immediately after the receipt of this Alert Service Bulletin and the changed life limits

must be entered in the list of life–limited parts and in the log card of the intermediate

transmission.

(2) If the revised allowable life limit has already been exceeded, only a ferry flight up to a

maximum of 20 fh to the maintenance facility is allowed. After this the component must

be replaced.

(3) For intermediate gear boxes fitted with the affected bevel gears, P/N 4639 310 065, that

have not reached the revised allowable life limit the gear boxes may remain in service

until life limit of the bevel gear is reached. The intermediate gear box must be sent to

a certified overhaul facility for bevel gear replacement.

This document is available on the internet: www.eurocopter.com/techpub
ALERT SERVICE BULLETIN

MBB BK117 C-2

MBB BK117 C-2-04A-005

PAGE 2 of 5 REVISION 02, 2010-04-28

2009-06-08

F. Approval

The technical content of this document is approved under the authority of DOA No.

 EASA.21J.034.

G. Manpower

Not applicable.

H. Weight and Balance

Not applicable.

I. Electrical Load Data

Not applicable.

J. Software Accomplishment Summary

Not applicable.

K. References

Not applicable.

L. Other publications affected

Not applicable.

M. Interchangeability of Parts

Not applicable.

2. Material Information

A. Material – Price and Availability

Not applicable.

B. Support Information

Not applicable.

C. Material Necessary for Each Helicopter

Not applicable.

D. Material Necessary for Each Spare

Not applicable.
ALERT SERVICE BULLETIN

MBB BK117 C-2

MBB BK117 C-2-04A-005

PAGE 3 of 5

2009-06-08

REVISION 02, 2010-04-28

E. Reidentified Parts

Not applicable.

F. Special Tooling

Not applicable.

3. Accomplishment Instructions

A. Determine serial number of the bevel gears 4639 310 065 installed in the intermediate

transmission by consulting the log card of the intermediate transmission.

(1) If a bevel gear with one of the serial numbers given in Table 1 is installed, take the

associated life limit from the Table and make the following entry:

(a) In the log card of the intermediate transmission: 

”I.A.W. ASB MBB BK117 C-2-04A-005 Bevel gear S/N XXXX must be replaced by

XXXX fh TSN”.

(b) In the list of life–limited parts: 

Life limit of bevel gear 4639 310 065 with S/N xxxx is xxxx fh.

(2) Copy reply form sheet on page 5, fill out and send to ECD.

(3) If the bevel gear S/N is not listed in Table 1, make the following entry:

In the log card of the intermediate transmission: 

”I.A.W. ASB MBB BK117 C-2-04A-005 bevel gear is not affected by this bulletin”.

4. Appendix

Table 1: Assignment of bevel gear’s S/N to life limit

Reply form sheet
ALERT SERVICE BULLETIN

MBB BK117 C-2

MBB BK117 C-2-04A-005

PAGE 4 of 5 REVISION 02, 2010-04-28

2009-06-08

Table 1: Assignment of bevel gear’s S/N to life limit

Bevel gear S/N Life limit (Fh) Bevel gear S/N Life limit (Fh)

1012 3400 1091 1500

1015 3400 1092 1500

1016 3400 1093 1500

1023 3400 1094 1500

1026 2900 1095 1500

1028 2900 1096 1500

1029 2900 1097 1500

1031 2900 1098 1500

1035 2900 1099 1500

1037 2900 1100 1500

1038 2900 1101 1500

1039 2900 1102 1500

1040 2900 1103 1500

1041 2900 1104 1500

1043 2900 1108 1500

1044 2900 1113 1500

1045 2900 1128 1500

1048 1500 1129 1500

1049 1500 1130 1500

1050 1500 1145 1500

1051 1500 1148 1500

1053 1500 1154 3400

1054 1500 1156 3400

1055 1500 1157 3400

1056 1500 1158 3400

1057 1500 1159 3400

1059 1500 1160 3400

1061 1500 1161 3400

1062 1500 1162 3400

1063 1500 A1162 4100

1065 1500 1163 3400

1066 1500 1164 3400

1067 1500 A1164 4100

1068 1500 1165 3400

1069 1500 1166 3400

1070 1500 1167 3400

1072 1500 1168 3400

1073 1500 1169 3400

1074 1500 1170 3400

1075 1500 1171 3400

1076 1500 1172 3400

1077 1500 1173 3400

1078 1500 1174 3400

1079 1500 A1174 4100

1080 1500 1175 3400

1082 1500 1176 3400

1084 1500 1177 4100

1085 1500 1178 4100

1086 1500 1179 4100

1087 1500 4004 4100

1089 1500

1090 1500
ALERT SERVICE BULLETIN

MBB BK117 C-2

MBB BK117 C-2-04A-005

PAGE 5 of 5

2009-06-08

REVISION 02, 2010-04-28

Telefax

To

Eurocopter Deutschland GmbH

Customer Support

FAX 0049 906 714111

Operator’s address:

Date:__________ Signature:___________________

Accomplishment Confirmation Form 

In order to be able to ensure an on–time availabilty of the bevel gears, we need your

support. Therefore, we ask you to fill out this reply form sheet and send it to ECD. 

Thank you!

The following helicopter is affected by ASB MBB BK117 C-2-04A-005:

Please make a copy of this page! The original of this page is to remain in the ASB!

Helicopter S/N:

Intermediate 

transmission S/N:

TT intermediate

transmission:

Flight hours per

year approx.:

Bevel gear S/N: Bevel gear TSN: